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Cons
It will not improve anything
It will clutter up the engine bay
It looks ugly
Waste of money
people will think your engine blows oil (broken engine)
It will increase the amount of oil that blows out of the engine
It will fill the engine internal baffles with oil over time
It will rise crankcase pressure causing more oil leaks over time
It will increase blow-by causing more rapid sludging of the oil and increased carbon deposits.
Pros
You supported a business somewhere that sells an unnecessary product
And I have the education and experience to back up my claims. I can also fill this page with quotes from GM engineer and experienced tuners who will say the same thing if you like. As well as other corvetteforum/supraforums/hptuners/zilvia/thirdgen/yellowbullet/theturboforums/etc... posts where I educate these details. I am merely trying to keep the posts short and to the point. People complain I type too much. But its either, I type too much information, or, nobody will believe the short posts because they lack information. The topic of PCV involves chemistry and engineering concepts such as partial pressure, gas density, streamlines, mean free path, bernoulli's, hydrocarbon byproducts, scalar pressure, molecular vectors, dissolved gasses, oil droplet radius and diameter formation, kinetic energy, turbulence/disorganization, etc...
I am willing to educate and post as many details as you need to learn the system but I won't do it without being asked. So ask or ...
Like all things it depends. Some engines desperately need an air oil separator. Porsche uses them from the factory for example on their wet sump H6 engines. Dry sump engines are less prone to requiring it.
ARRRGH! Not again. This has been beat to death at least since the C5s. Do an "Advanced search" across any/all of those forums, and find that about an equal number of Forum members swear by them and at them. So, do what YOU think is right... or flip a coin.
Like all things it depends. Some engines desperately need an air oil separator. Porsche uses them from the factory for example on their wet sump H6 engines. Dry sump engines are less prone to requiring it.
All engines have oil/air separator. That is called a baffle and it is inside both valve covers. Their job is to utilize the kinetic energy of pcv gas to separate liquid oil droplets of specific radius range from the gas and allow them to drain back into the engine. The problem with catch cans and other modifications is they add friction and turbulence to the PCV gas which interferes with the OEM baffle (OEM air/oil separator) which causes more oil to blow from the engine. The separator is designed to work with a specific kinetic energy and oil droplet size range in mind. Since crankcase pressure controls oil droplet radius and oil droplet density,
-simply adjust pressure in the above equations and see what happens to the droplet radius and density of oil droplets.
Now imagine you have a perfectly good engine oil/air separator inside the OEM valve cover, and reduce the kinetic energy of gas leaving the valve cover by lengthening the hose (or adding volume). The energy reduction causes pressure to increase. Now you have larger oil droplets and more oil density and oil blows out of the crankcase.
And that is just the beginning of the problem you've created. Now the piston rings switch early at the end of power stroke and blow-by gas carries oil into the ring packs. Soon the rings will begin to stick and seize as light hydrocarbons leave the pack and heavy chains stick and glue the rings still. Now burning oil is being pulled into the combustion chamber and crankcase begins to smoke and cylinder walls begin to wear excessively.
Sure it happens after 50k 80k maybe 100k miles. By which time you assume the engine is just tired and worn out- you have no idea it was that PCV modification you made back when that caused the eventual wear and failure.
All engines have oil/air separator. That is called a baffle and it is inside both valve covers. Their job is to utilize the kinetic energy of pcv gas to separate liquid oil droplets of specific radius range from the gas and allow them to drain back into the engine. The problem with catch cans and other modifications is they add friction and turbulence to the PCV gas which interferes with the OEM baffle (OEM air/oil separator) which causes more oil to blow from the engine. The separator is designed to work with a specific kinetic energy and oil droplet size range in mind. Since crankcase pressure controls oil droplet radius and oil droplet density,
-simply adjust pressure in the above equations and see what happens to the droplet radius and density of oil droplets.
Now imagine you have a perfectly good engine oil/air separator inside the OEM valve cover, and reduce the kinetic energy of gas leaving the valve cover by lengthening the hose (or adding volume). The energy reduction causes pressure to increase. Now you have larger oil droplets and more oil density and oil blows out of the crankcase.
And that is just the beginning of the problem you've created. Now the piston rings switch early at the end of power stroke and blow-by gas carries oil into the ring packs. Soon the rings will begin to stick and seize as light hydrocarbons leave the pack and heavy chains stick and glue the rings still. Now burning oil is being pulled into the combustion chamber and crankcase begins to smoke and cylinder walls begin to wear excessively.
Sure it happens after 50k 80k maybe 100k miles. By which time you assume the engine is just tired and worn out- you have no idea it was that PCV modification you made back when that caused the eventual wear and failure.
My example of Porsche leverage an external air oil separator in addition to any internal crankcase design. Subaru as a similar horizontal engine that lacks an AOS are prone to push massive amounts of oil the wrong direction and into the intake stream. My LT1 + dry sump doesn't push massive oil into the intake. My Subaru's and Honda do and all have AOS with drainback to the crankcase with PCV valve elimination.
My example of Porsche leverage an external air oil separator in addition to any internal crankcase design. Subaru as a similar horizontal engine that lacks an AOS are prone to push massive amounts of oil the wrong direction and into the intake stream. My LT1 + dry sump doesn't push massive oil into the intake. My Subaru's and Honda do and all have AOS with drainback to the crankcase with PCV valve elimination.
There isn't any one solution. It all depends.
Air oil separation is one necessary part of the total solution but has nothing to do with PCV. The term 'PCV' Literally means "positive crankcase ventilation" which has nothing to do with separating air and oil. Oil induction is only a small fraction of the problem posed by blow-by gas. If the only issue was oil/air separation then a catch can would be fine solution, just catch the oil and be done. This is the biggest mistake you can make, thinking that PCV is just about venting the pressure and catching the oil when it has nothing to do with that. That is the mistake people have made for 30 years mechanics, tuners, all of them. They put giant lines and a big can on the engine and that is NOT a PCV system, it defeats PCV and contaminates the engine ruining it eventually.
The real issue is blow-by gas contamination, deposits, leaks, eventual wear and failure. And there is more. Piston ring function declines, piston rings stick and wear, ring pack contamination. Rapid sludging and dilution of engine oil. Blow-by gas is a contaminant and needs to be actively pulled out somehow.
Catching the oil will not fix these issues.
The proper way to address these issues is by PCV.
PCV means having two things if I can say so simply,
1. Streamlines which are able to rapidly collect/capture blow-by gas by giving them consolidated velocity vectors as they leave the ring packs during WOT/IDLE/CRUISE
2. A pressure below atmospheric at all times during engine operation.
The OEM of all factory engines in the world achieves these two goals, more or less, some better than other I'm sure but all of them nevertheless achieve to some degree these 2 simple points. Adding a catch can will make them both worse off because of friction and fluid mass, it takes energy to move fluids and lines/hoses/volume create additional friction and can volume induct turbulence. They all work against PCV which will increase the rate of engine wear and failure.
The oil separation is always achieved using a baffle system. All engines have baffles of course inside. Some maybe outside, but its rare. And sometimes something outside looks like a baffle isn't really what you think it is. For example sr20det 2.0L turbo has an 'outside baffle' but the way it works is opposite how most people think by inspection, it prevent oil from being pulled out of the crankcase as opposed to capturing and returning oil to the crankcase.
The problem with catch cans and other modifications is they add friction and turbulence to the PCV gas which interferes with the OEM baffle (OEM air/oil separator) which causes more oil to blow from the engine.
Air oil separation is one necessary part of the total solution but has nothing to do with PCV. The term 'PCV' Literally means "positive crankcase ventilation" which has nothing to do with separating air and oil. Oil induction is only a small fraction of the problem posed by blow-by gas. If the only issue was oil/air separation then a catch can would be fine solution, just catch the oil and be done. This is the biggest mistake you can make, thinking that PCV is just about venting the pressure and catching the oil when it has nothing to do with that. That is the mistake people have made for 30 years mechanics, tuners, all of them. They put giant lines and a big can on the engine and that is NOT a PCV system, it defeats PCV and contaminates the engine ruining it eventually.
The real issue is blow-by gas contamination, deposits, leaks, eventual wear and failure. And there is more. Piston ring function declines, piston rings stick and wear, ring pack contamination. Rapid sludging and dilution of engine oil. Blow-by gas is a contaminant and needs to be actively pulled out somehow.
Catching the oil will not fix these issues.
The proper way to address these issues is by PCV.
PCV means having two things if I can say so simply,
1. Streamlines which are able to rapidly collect/capture blow-by gas by giving them consolidated velocity vectors as they leave the ring packs during WOT/IDLE/CRUISE
2. A pressure below atmospheric at all times during engine operation.
The OEM of all factory engines in the world achieves these two goals, more or less, some better than other I'm sure but all of them nevertheless achieve to some degree these 2 simple points. Adding a catch can will make them both worse off because of friction and fluid mass, it takes energy to move fluids and lines/hoses/volume create additional friction and can volume induct turbulence. They all work against PCV which will increase the rate of engine wear and failure.
The oil separation is always achieved using a baffle system. All engines have baffles of course inside. Some maybe outside, but its rare. And sometimes something outside looks like a baffle isn't really what you think it is. For example sr20det 2.0L turbo has an 'outside baffle' but the way it works is opposite how most people think by inspection, it prevent oil from being pulled out of the crankcase as opposed to capturing and returning oil to the crankcase.
What is your solution to baffles that do not keep large amounts of oil from entering the intake via this vacuum line?
Well its a can. It can stop liquids, such as suspended oil droplets. But the OEM baffles are designed and tested at OEM pressure crankcase numbers such that a pre-determined size range and mass of oil is ejected which can suitably sustain the engine for a lifetime of 20+ years 200k+ miles as evinced by completely untouched OEM engines which have achieved this kind of mileage. The modifications people make to engines without properly addressing the crankcase pressure are what cause the issues people complain about; Often an "OEM" engine has an aftermarket air filter or lack of maintenance to it's PCV system such as old leaking hoses cracked or a clogged PCV valve and so forth.
I've never met or seen an engine no matter how many miles which was properly maintained that couldn't be washed, cleaned, restored to clean operating conditions with OEM pcv equipment set to OEM pressure ranges.
What is your solution to baffles that do not keep large amounts of oil from entering the intake via this vacuum line?
You mean OEM baffles? I've tuned hundreds of engines- perhaps around one thousand engines since 1996~. Majority of them turbo, so name a few, 1zz, sr20det, 3sgte, 2jz-gte, RB26dett, 4g63, VR6, 02-07 LS including many truck variants, ca18, ka24, k20a, &c
Many of them come factory turbo. Some are just plain old truck engines or car engines converted to turbo. As you may well know adding forced induction is notorious for increasing blow-by and making crankcase PCV systems even more difficult to deal with.
In every single case, no matter what the engine type, I have never had a problem with oil blowing out of the engine once the PCV was properly measured and setup to OEM standards; That is, streamlines for evacuation and approx 0.8" to 1.5" Hg of vacuum at WOT. If you can meet these simple conditions by setting the crankcase pressure properly, then the OEM baffles will meet OEM criterion this is how they are tested, and there won't be any issues with oil leaking or oil blowing out of the engine. The only time oil should blow from an engine is when the piston is damaged and blow-by forces large compression pressure into the crankcase which causes high crankcase pressure to blow oil out of the engine. In this case, a catch can may be used to temporarily bandaid the engine so it can drive for a little while before the piston is replaced. That is the purpose of catch cans, when I see one, I think of a blown up engine. The same goes for engines built improperly for example bore-ing an engine without a deck plate, excessive piston-wall clearance, running an engine with forged piston hard before the pistons fully expanded in the bores, these all create 'broken piston' symptoms and excessive blow-by due to user error.
06-20-2023, 02:35 PM
Should I get a Catch Can?
